A vehicle using an internal combustion engine using gasoline or heavy oil as main fuel has negative impact on pollution such as air pollution, or the like. Therefore, to reduce the occurrence of the pollution, an electric vehicle or a hybrid vehicle which are operated by electrical energy output from a battery system have recently been developed. The battery system of the electric or hybrid vehicle may include a battery in which a plurality of battery cells are connected in series-parallel to store and provide energy.
In addition, since the plurality of battery cells repeatedly perform a charging and a discharging, the battery cells need to be managed to maintain an appropriate operation state and performance by efficiently adjusting the charging/discharging. Accordingly, a battery management device or a battery management system (BMS) configured to perform an algorithm for managing and operating the battery is provided. The BMS is configured to measure a current, a voltage, a temperature, and the like of the battery to estimate a state of charging (SOC) of the battery based on the measured current, voltage, and temperature, and controls the SOC to improve fuel consumption efficiency. To accurately control the SOC, the SOC of the battery performing the charging/discharging requires accurate estimation.
According to a method for estimating the SOC of the battery, the SOC of the battery is varied based on the temperature of the battery. In particular, there are problems that in a low temperature region or as the temperature of the battery is a low temperature, the SOC of the battery decreases to less than a target SOC of the battery, a drive distance of the vehicle is reduced due to a battery state which is not fully charged at the time of charging the battery, and a charging time of the battery is also increased.